A bird in the hand is worth two in the bush.
The saying above simply means be happy with what you have. Stop and appreciate the positives instead of focusing on the negatives.
Science proves the repetition of thoughts and emotions in our brain creates lasting connections. Those connections subconsciously drive our emotional well-being. Just like a runner trains for a marathon or an Olympic athlete perfects competition form, our brains must be trained. How you train it, is your choice!
P.S. I love my birds!